There are many problems with having no human interaction in firing a weapon. One of the largest is if someone is smart, they can hack these robots and have them turn on those they are supposed to be guarding. Another problem is that under certain conditions, passwords can be garbled to robot but clear to a human. And third problem is that humans have this funny thing called intution that allows us to judge the intent of a person, a robot can not do this. The idea of having robots on border guard is pretty smart; as long as they are armed with non-lethal weapons only. Use rubber bullets, tear gas, tranquilizers, mono directional white noise generators, etc. instead of bullets. Doing this would be just as effective as arming the robot with a gun.